1981020109 has 2 divisors, whose sum is σ = 1981020110. Its totient is φ = 1981020108.

The previous prime is 1981020031. The next prime is 1981020127. The reversal of 1981020109 is 9010201891.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1936264009 + 44756100 = 44003^2 + 6690^2 .

It is a cyclic number.

It is not a de Polignac number, because 1981020109 - 2⁷ = 1981019981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1981021109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 990510054 + 990510055.

It is an arithmetic number, because the mean of its divisors is an integer number (990510055).

Almost surely, 2^1981020109 is an apocalyptic number.

It is an amenable number.

1981020109 is a deficient number, since it is larger than the sum of its proper divisors (1).

1981020109 is an equidigital number, since it uses as much as digits as its factorization.

1981020109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 1981020109 is about 44508.6520690079. The cubic root of 1981020109 is about 1255.9228481573.

The spelling of 1981020109 in words is "one billion, nine hundred eighty-one million, twenty thousand, one hundred nine".